<?php
class Captcha {
    protected $code;
    protected $width = 35;
    protected $height = 150;

    function __construct() {
        $this->code = substr(sha1(mt_rand()), 17, 6);
    }

    function getCode(){
        return $this->code;
    }

    function showImage() {
        $image = imagecreatetruecolor($this->height, $this->width);

        $width = imagesx($image);
        $height = imagesy($image);

        $black = imagecolorallocate($image, 0, 0, 0);
        $white = imagecolorallocate($image, 255, 255, 255);
        $red = imagecolorallocatealpha($image, 255, 0, 0, 75);
        $green = imagecolorallocatealpha($image, 0, 255, 0, 75);
        $blue = imagecolorallocatealpha($image, 0, 0, 255, 75);

        imagefilledrectangle($image, 0, 0, $width, $height, $white);

        imagefilledellipse($image, ceil(rand(5, 145)), ceil(rand(0, 35)), 30, 30, $red);
        imagefilledellipse($image, ceil(rand(5, 145)), ceil(rand(0, 35)), 30, 30, $green);
        imagefilledellipse($image, ceil(rand(5, 145)), ceil(rand(0, 35)), 30, 30, $blue);

        imagefilledrectangle($image, 0, 0, $width, 0, $black);
        imagefilledrectangle($image, $width - 1, 0, $width - 1, $height - 1, $black);
        imagefilledrectangle($image, 0, 0, 0, $height - 1, $black);
        imagefilledrectangle($image, 0, $height - 1, $width, $height - 1, $black);
         
        imagestring($image, 10, intval(($width - (strlen($this->code) * 9)) / 2),  intval(($height - 15) / 2), $this->code, $black);

        header('Content-type: image/jpeg');

        imagejpeg($image);

        imagedestroy($image);
    }
}
?>